I can change it to where the vampire just might be powerful among his kind and not actually a king, but hiding in the countryside of japan during the warring state era if that would work better with the setting and time period. The character I have in mind is a flexible one, so I can change his history as needed. I have never done a samurai roleplay though.
If we did change it to wounded knight x savior and adjusted the time period and setting, I would not mind being the vampire. Though the last time I used the character I have in mind, it was a m/m/m roleplay with twin vampire royals.